How to Compress a PDF for Email Without Uploading It
Most oversized PDFs are full of scans and photos. Here's how to shrink them in your browser, which level to choose, and how small an email attachment needs to be.
You attach a PDF, press send, and the email bounces or your mail app refuses the file. Most of the time the PDF isn't long, it's heavy: a few scanned pages or photos can make a ten-page document weigh more than a whole book of text. The fix is to shrink the images inside it, which you can do in your browser in under a minute, without uploading the file anywhere.
Why is my PDF so big?
Text is tiny. A page of words takes a few kilobytes. Images are what make PDFs large:
- Scanned documents. Every scanned page is a photo of the paper, often saved at a much higher resolution than anyone needs to read it.
- Phone photos. Receipts, IDs or homework photographed on a phone and turned into a PDF bring along the camera's full resolution, often 3,000 or 4,000 pixels across.
- Reports and slides with pictures. One high-resolution chart or photo per page adds up quickly.
So "compressing a PDF" really means making those images smaller while leaving the text alone.
How to compress a PDF in your browser
- Open the Compress PDF tool and select your file.
- Choose a level. Balanced is the right starting point for email and upload forms.
- Click Compress and Download. The tool shows the old and new size, for example "7.1 MB → 653 KB, 91% smaller", and downloads the smaller copy.
The file is read and rebuilt by your browser on your own device. Nothing is sent to a server, which matters for the documents people most often need to shrink: tax forms, medical records, contracts and IDs.
Which level should you pick?
| Level | What it does | Good for |
|---|---|---|
| Light | Re-saves photos and scans at high quality and only shrinks very large ones (over 2,400 pixels on the longest side). | Documents you may print, or when you only need a little off the size. |
| Balanced | Keeps images up to 1,800 pixels and also converts photo-like images that were stored inefficiently. | Email, upload portals, job and school applications. |
| Strong | Keeps images up to 1,200 pixels at a lower quality setting. | The smallest possible file, for reading on screen. |
In our own test, a 7.1 MB report made mostly of photos came out at about 4.7 MB on Light, 650 KB on Balanced and 190 KB on Strong, with all of its text still selectable. Your results depend on what the PDF contains, so if Balanced isn't small enough, run the original through Strong.
What stays the same
- Text stays sharp. Words in a PDF aren't images, so they aren't touched. You can still select, search and copy them.
- Charts, diagrams and screenshots are left alone. Images made of a few flat colours would turn blotchy as JPEG, so the tool skips them.
- Links and page layout don't change. Pages stay in the same order and size.
Two honest limits. A PDF that is mostly text is already small, so it may shrink only a little; if it can't get meaningfully smaller, the tool says so and doesn't download a copy. And a digitally signed PDF loses its signature when it's changed, as it would with any edit, so compress before signing rather than after.
Check it before you send it
Thirty seconds of checking saves an awkward follow-up email:
- Open the compressed copy and zoom into the smallest print on a scanned page, such as a signature, a date or an ID number. If it's hard to read, compress the original again on Light or Balanced.
- Check that the page count matches the original.
- Keep the original file. Compression is one-way, so if you ever need the full-quality version, you want the untouched copy.
How small does it need to be?
Each email service sets its own limit for a message and its attachments:
- Gmail: 25 MB for personal accounts. Above that, Gmail replaces the attachment with a Google Drive link instead, according to Google. Work and school accounts follow limits set by their administrator.
- Outlook: when sending from the Outlook app, the limit is 20 MB for internet accounts such as Outlook.com and 10 MB by default for business (Exchange) accounts, counting the whole message, according to Microsoft.
Attachments are encoded for sending, which adds roughly a third to their size, so leave some room below the limit. Upload forms for applications and government portals often have much smaller limits, such as 2 MB or 5 MB; the form itself will say.
Still too big?
- Send it in parts. Use Split PDF to save pages 1–20 as one file and 21–40 as another, then attach them to separate emails.
- Drop pages you don't need. Split PDF also works the other way: keep only the pages that matter, such as the signed page and the summary.
- Share a link. For very large files, upload to a cloud drive you already use and send the link.
- Scan smaller next time. Most scanning apps have a document or lower-resolution setting, which gives smaller files from the start.
If you're putting several documents together first, merge them into one PDF, then compress the merged file so you only have one attachment to send.
Frequently asked questions
Will compressing a PDF reduce its quality?
Only the images inside it change. Light keeps them closest to the original, while Strong makes them noticeably softer when you zoom in. Text, links and layout stay exactly as they were.
Why didn't my PDF get smaller?
If it's mostly text, there is very little to compress. The tool tells you when a PDF is already compact and doesn't download an unchanged copy.
Can I compress a password-protected PDF?
Not directly. Remove the password in the app that created the file, then compress the unlocked copy.